Aerosol dispenser with flow diverter

ABSTRACT

An aerosol dispenser, for example an inhaler, consists of a container (12) containing a propellant and a medicament, with a valve (14), and an applicator (16). The applicator includes a frusto-conical diverter (20) with a small orifice (60) facing the valve orifice (37). Aerosol droplets predominantly pass through the small orifice, decelerate, and can then be inhaled, while the propellant gas is predominantly diverted out of the applicator.

This invention relates to an aerosol dispenser and particularly but notexclusively an aerosol inhaler, that is a device for dispensing amedicament or therapeutic agent in the form of an aerosol to be inhaledby a patient or user.

Such inhalers are customarily used in the treatment of asthma and ofhay-fever. Known inhalers comprise a container with a valve, thecontainer containing a medicament and a liquefied propellant gas, andthe valve being such that when it is depressed by the user, a fine mistor aerosol of droplets of the medicament is emitted. The droplets arethen inhaled. One such inhaler, in which the valve is arranged to emit ametered dose of the medicament, is described in UK Patent GB 830 427(Riker Labs. Inc.). A problem with known inhalers is that the dropletsare emitted at a very high velocity, which may exceed 40 m/s, and sotend to impact on the back of the throat rather than being carried withinhaled air into the lungs.

According to the present invention there is provided an aerosoldispenser including an aerosol-emitting valve and an applicator throughwhich aerosol droplets pass after emission, the applicator comprising afrusto-conical diverter defining at one end a small orifice alignedfacing the valve, such that in use the aerosol droplets predominantlypass through the orifice while the gas stream entraining the dropletspredominantly is diverted by the diverter.

The droplets pass through the orifice due to their momentum, and arethen in a region of still air in which they soon lose their highvelocity. The dispenser may be an inhaler, in which case in use theother end of the applicator would be adjacent to a user's mouth. If theuser inhales air within the applicator, the droplets are carried alongwith the air into the lungs as desired.

Desirably the applicator also includes a shield or guard to deflect thediverted gas stream from the user's face, so it is deflected to adirection at least 90 degrees from the direction followed by theundiverted aerosol droplets.

The dimensions of the applicator are preferably such that the gas streamthrough the orifice is less than 10 percent, desirably less than 5percent, of the emitted gas stream. The exact dimensions depend upon thesize of the droplets which it is desired to inhale, as the smallestdroplets will be carried away with the predominant gas stream.

The invention will now be further described, by way of example only, andwith reference to the accompanying drawing, which shows an aerosolinhaler 10. The inhaler 10 includes a container 12 with a dose-meteringvalve 14; and an applicator 16 including a cap 17 and sleeve 18, adiverter 20 and a mouthpiece 22, integral with each other. The container12 contains a solution or a suspension of an active therapeutic agent ina liquid 24 consisting principally of a propellant comprising a 70/30%mixture of dichlorodifluoromethane and trichlorofluoromethane, whichalso provides a vapour phase 26, and which maintains a vapour pressuretypically between about 2 and 4 atmospheres. It will be appreciated thatother propellants may be used.

Sealed to the container 12 by an annular gasket 32, is a lid portion 30which supports the dose-metering valve 14, a valve stem 34 protrudingthrough the centre of the lid portion 30. The outer portion 35 of thevalve stem 34 is hollow and mates with a stepped recess in an end piece38 fixed inside the lid 17, so as to communicate through a narroworifice 36 (of diameter 0.5 mm) with a conical expansion orifice 37defined in the end-piece 38. A small hole 39 is provided through thewall of the hollow portion 35. Above the lid portion 30 (as shown) is agenerally cylindrical metering chamber 40. The valve stem 34 extendsthrough the chamber 40, passing through a diaphragm seal 42 adjacent thelid portion 30 and through a metering chamber seal 44 at the upper endof the chamber 40. The seals 42 and 44 permit the valve stem 34 to slideup or down, and the stem 34 is resiliently biassed into the positionshown by a compression spring 46 within the chamber 40 acting between awasher 47 adjacent the seal 44 and a flange 48 fixed to the valve stem34. The valve stem has a groove 50 on one side near its upper end, whichin the position shown provides fluid communication through the seal 44and the washer 47 to the inside of the chamber 40. A retaining cup 52fits tightly around the outside of the chamber 40, defining a chamber 53into which the upper end of the valve stem 34 moves when the stem ispressed up. The chamber 53 communicates with the bottom (as shown) ofthe container 12 through one or more passages 54 defined by grooves inthe inside wall of the cup 52.

The applicator 16 is removable from the container 12 and its valve 14.The two parts of the inhaler 10 are assembled by carefully sliding thesleeve 18 over the lid portion 30, until the hollow portion 35 of thevalve stem 34 mates with the recess in the end piece 38. The diverter 20is of frusto-conical shape, defining a small orifice 60 of diameterabout 2 mm facing the expansion orifice 37. Parts of the sleeve 18 andthe cap 17 are cut away to define an aperture 62 for aerosol emittedfrom the orifice 37, and the diverter 20 is joined to the sleeve 18 andthe cap 17 by three equally-spaced thin stays 64 (only two are shown) sothat the distance from the expansion orifice 37 to the small orifice 60is about 25 mm. The wider end of the diverter 20 joins to the mouthpiece22, which is cylindrical and coaxial with the diverter 20, and aroundthe wider end of the diverter 20 there is also a curved annular baffleor shield 66.

As shown, the metering chamber 40 is full of the liquid 24,communicating as it does with the container 12 via the passages 54, thechamber 53, and the valve groove 50. When the inhaler 10 is to be used,the user places the mouthpiece 20 in his mouth and pushes the container12 downwardly relative to the applicator 16. The valve stem 34consequently slides up into the chamber 53, so the seal 44 preventscommunication between the chambers 53 and 40. Then, once the small hole39 is above the seal 42, the contents of the metering chamber 40 flowthrough the hollow portion 35, the narrow orifice 36 and the expansionorifice 37, as the propellant evaporates. A fine spray or aerosol ofdroplets of the active agent consequently emerges at high speed towardsthe diverter 20.

When this aerosol impinges on the diverter 20, the propellant gases arediverted to flow outside it, and are then deflected away from the user'sface by the baffle 66. The droplets on the other hand, due to theirmomentum, continue substantially along their initial trajectories, sopassing through the small orifice 60 into the relatively calm air insidethe diverter 20 and the mouthpiece 22. Here they rapidly decelerate. Theuser then breathes in the air within the diverter 20 and the mouthpiece22, so inhaling the droplets.

It will be appreciated that the detailed features of the valve 14 arenot an aspect of the present invention, and that the applicator 16 couldbe used with containers with different types of valve mechanism, forexample those used the other way up and provided with a dip tube insteadof the retaining cap 52. It will also be appreciated that the shape andsize of the diverter 20 and the small orifice 60, and its separationfrom the expansion orifice 37, might differ from those described here.It will be understood that the applicator 16 can be used with aerosolcontainers for non-medical aerosols.

I claim:
 1. An aerosol dispenser including an aerosol-emitting valve andan applicator through which aerosol droplets pass after emission, theapplicator comprising a frusto-conical diverter defining at one end asmall orifice aligned facing the valve, such that in use the aerosoldroplets predominantly pass through the orifice while the gas streamentraining the droplets predominantly is diverted by the diverter.
 2. Anaerosol dispenser as claimed in claim 1 wherein the applicator alsocomprises a shield arranged such that in use the diverted gas stream isdeflected to a direction at least 90 degrees form the direction followedby the undiverted aerosol droplets.
 3. An aerosol dispenser as claimedin claim 1 wherein the dimensions of the applicator are such that in usethe gas stream through the orifice is less than ten percent of theemitted gas stream.
 4. An aerosol dispenser as claimed in claim 3wherein the dimensions of the applicator are such that in use the gasstream through the orifice is less than five percent of the emitted gasstream.
 5. An aerosol dispenser as claimed in claim 1 wherein theapplicator also comprises means to define an open-ended chamber furtherfrom the valve than the diverter, into which the orifice communicates.6. An aerosol dispenser as claimed in claim 5 wherein the chamber is ofcylindrical form, and is coaxial with the longitudinal axis of thediverter.